Ab $\textit{initio}$ investigations of magnetic properties of ultrathin transition-metal films on $\textit{4d}$ substrates

Al-Zubi, Ali

Dissertation / PhD Thesis/Book

Ab $\textit{initio}$ investigations of magnetic properties of ultrathin transition-metal films on $\textit{4d}$ substrates

Al-Zubi, A. (corresponding author)FZJ*

2010
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-89336-641-5

Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Schriften des Forschungszentrums Jülich. Schlüsseltechnologien / Key Technologies 16, II, 143 S. (2010) = RWTH Aachen, Diss., 2010

Please use a persistent id in citations: http://hdl.handle.net/2128/3773

Abstract: In this thesis, we investigate the magnetic properties of 3$\textit{d}$ transition-metal monolayers on 4$\textit{d}$ transition-metal substrates by means of state of the art first-principles quantum theory. In contrast to previous investigations on noble metal substrates, the strong hybridization between 3$\textit{d}$ metals and the substrate is an additional parameter determining the properties. In order to reveal the underlying physics of these systems we study trends by performing systematic investigations across the transition-metal series. Case studies are presented for which Rh has been chosen as exemplary 4$\textit{d}$ substrate. We consider two substrate orientations, a square lattice provided by Rh(001) and a hexagonal lattice provided by Rh(111). We find, all 3$\textit{d}$ transition-metal (V, Cr, Mn, Fe, Co and Ni) monolayers deposited on the Rh substrate are magnetic and exhibit large local moments which follow Hund’s rule with a maximum magnetic moment for Mn of about 3.7 μ$_{B}$ depending on the substrate orientation. The largest induced magnetic moment of about 0.46 μ$_{B}$ is found for Rh atoms adjacent to the Co(001)-film. On Rh(001) we predict a ferromagnetic (FM) ground state for V, Co and Ni, while Cr, Mn and Fe monolayers favor a c(2 × 2) antiferromagnetic (AFM) state, a checkerboard arrangement of up and down magnetic moments. The magnetic anisotropy energies of these ultrathin magnetic films are calculated for the FM and the AFM states. With the exception of V and Cr, the easy axis of the magnetization is predicted to be in the film plane. With the exception of Fe, analogous results are obtained for the 3$\textit{d}$-metal monolayers on Rh(111). For Fe on Rh(111) a novel magnetic ground state is predicted, a doublerow- wise antiferromagnetic state along the [112] direction, a sequence of ferromagnetic double-rows of atoms, whose magnetic moments couple antiferromagetically from double row to double row. The magnetic structure can be understood as superposition of a left- and right-rotating flat spin spiral. In a second set of case studies the properties of an Fe monolayer deposited on varies hexagonally terminated hcp (0001) and fcc (111) surfaces of 4$\textit{d}$-transition metals (Tc, Ru, Rh, to Pd) are presented. The magnetic state of Fe changes gradually from noncollinear 120$^{◦}$ Néel state for Fe films on Tc, and Ru, to the double-row-wise antiferromagnetic state on Rh, to the ferromagnetic one on Pd and Ag. The noncollinear state is a result of antiferromagnetic intersite exchange interactions in combination with the triangular lattice provided by the hexagonal surface termination of the (111) surfaces. A similar systematic trend is observed for a Co monolayer on these substrate, but shifted towards ferromagnetism equivalent to one element in the periodic table. [...]

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